In the rotation support portion of various machines such as a transmission for use in a car, there is mounted a thrust roller bearing. For example, in the case of the car transmission, between a step portion provided in a rotary shaft and the axial end face of a gear disposed in the periphery of the rotary shaft, there is mounted a thrust roller bearing, whereby, while the thrust roller bearing is used to support a thrust load applied between the rotary shaft and gear, the thrust roller bearing allows the rotary shaft and gear to rotate relative to each other. In order to enhance the mounting performance of such thrust roller bearing, conventionally, as disclosed in, for example, the Patent Document 1 and 2, there is known a structure for securing the race of the thrust roller bearing to its mating member. FIGS. 15 and 16 respectively show the examples of the conventional structure which are disclosed in the Patent Document 1 and 1 respectively.
Firstly, in FIG. 15, as the first example of the conventional structure, there is shown a structure which is disclosed in the Patent Document 1. A thrust roller bearing 71 includes a cage 72, a plurality of rollers 73, 73, and a race 74. The cage 72 is formed by bending a metal plate to have an annular shape as a whole, and has a plurality of pockets 75, 75 arranged at a plurality of locations along the circumferential direction such that they are respectively oriented in the radial direction (radially arranged). The rollers 73, 73 are slidably held within the pockets 75, 75 respectively. The race 74 can be formed by bending a metal plate. The race 74 includes an annular race portion 76 with which the rolling surfaces of the respective rollers 73, 73 can be rollingly contacted, and a cylindrical portion 77 which is curved from the outer circumferential edge of the race portion 76 toward the side where the respective rollers 73, 73 are to be disposed.
A locking portion 78, which can be formed by bending the distal edge of the cylindrical portion 77 toward the inside diameter side of the bearing 71, is engaged with the outer circumferential edge of the cage 72, whereby the cage 72 and race 74 are prevented from being separated from each other. In the inner circumferential edge of the race 74, there is formed a support cylindrical portion 79 which is bent in the opposite direction to the cylindrical portion 77 with respect to the axial direction of the race portion 74. Further, at a plurality of locations along the circumferential direction on the outer circumferential surface of the support cylindrical portion 79, there are formed fastening protrusions 80 respectively. On the other hand, in the inner circumferential surface of the end portion of a hollow shaft 81, that is, a mating member on which the thrust roller bearing 71 is mounted, there is formed a catching groove 82 such that it extends over the entire circumference. To mount the thrust roller bearing 71 onto the hollow shaft 81, the support cylindrical portion 79 may be fitted with the inner surface of the end portion of the hollow shaft 81 and also the respective fastening protrusions 80 may be engaged with the catching groove 82. In this state, the thrust roller bearing 71 is mounted on the hollow shaft 81 such that the former is prevented from being separated from the latter unexpectedly. This can facilitate the assembling or mounting operation of a rotary mechanical apparatus such as a transmission.
Next, FIG. 16 shows the second example of the conventional structure that is disclosed in the Patent Document 2. Specifically, a thrust roller bearing 71a according to the second conventional example includes a cage 72a, a plurality of rollers 73, 73 and a pair of races 74a, 74b. Similarly to the previously described first example, prevention of separation between one race 74a (the one on the right in FIG. 16) and the cage 72a is attained by a locking portion 78 which is formed in the distal edge of a cylindrical portion 77a formed in the outer circumferential edge of the outer race 74a. On the other hand, at a plurality of locations along the circumferential direction on the inner circumferential surface of a cylindrical portion 77b formed in the inner circumferential edge of the other race 74b (the one of the left in FIG. 16), there are formed fastening protrusions 80a respectively. In the outer circumferential surface of a shaft member 83 serving as a mating member on which the thrust roller bearing 71a is to be mounted, specifically, in such portion of the shaft member 83 outer circumferential surface as exists near to a step surface 84, there is formed a catching groove 82a such that it extends over the whole periphery of such portion. To mount the thrust roller bearing 71a onto the shaft member 83, the cylindrical portion 77b may be fitted with the outer surface of the shaft member 83 and also the respective fastening protrusions 80a may be engaged with the catching groove 82a. In this state, the thrust roller bearing 71a is mounted on the shaft member 83 such that the former is prevented from being separated from the latter unexpectedly. This can facilitate the mounting operation of a rotation-type mechanical apparatus such a transmission.
Also, between the impeller or turbine of a torque converter and the stator thereof, there is interposed a thrust roller bearing used to support a thrust load which is generated by hydraulic liquid flowing between the impeller and turbine. The stator, which serves as the support surface of the thrust race of the thrust roller bearing, is generally made of aluminum in view of reducing weight and improving fuel efficiency of a vehicle. Therefore, under the actual vehicle use environment, there is the following possibility. That is, due to the relative rotation between the stator and thrust race, the support surface of the stator can be worn; and, when such wear progresses, the proper dimensional relationship between the stator and thrust race can be lost, resulting in the trouble of the vehicle.
As measures against this trouble, in a thrust roller bearing 100 which is shown in FIG. 17 and is applied to a torque converter, there are provided a plurality of rotation preventing protrusions 102 on the outer periphery of its thrust race 101, and the rotation preventing protrusions 102 are respectively fitted into their associated hydraulic fluid grooves 104 formed in a stator 103, thereby preventing relative rotation between the stator 103 and thrust race 101 (see, for example, the Patent Document 3). Here, in the inner circumferential edge of the thrust race 101, there is formed a cylindrical portion 105 and, on the edge portion of the distal end of the cylindrical portion 105, a plurality of retaining projections 107 are formed by radially outward upsetting to prevent a cage 106 from falling out.
In addition, conventionally, there are further proposed a structure in which, in a cylindrical portion formed in the inner circumferential edge of the thrust race of a thrust roller bearing, there is formed a locking projection bent outwardly in the radial direction, thereby preventing rotation between the thrust roller bearing and its mating member(see, for example, the Patent Document 4); and, a structure in which, in the cylindrical portion of a thrust roller bearing, there is provided a projection, thereby preventing the thrust roller bearing and its mating member from moving in the axial direction relative to each other (see, for example, the Patent Document 5).